The present invention relates to fire retardant welts or the beading cords used in upholstery.
The furniture industry has been under self-imposed pressure to improve the fire resistance of upholstered furniture and, therefore, examined carefully the fire retardant characteristics of each component of upholstered furniture, including the welt cords. Foremost in this examination is the resistance to ignition by burning cigarettes or cigars which cause most upholstery fires.
There are two basic kinds of welt cords. One type is an extruded foam or solid plastic bead. The fire retardation characteristics of the plastic bead were increased by enclosing a wire within and along the length of the bead to help conduct heat away from a burning cigarette placed on the bead so that the plastic material near the burning cigarette will tend not to be heated to its ignition temperature. However, the plastic welt cord, even when foamed, is fairly hard to the touch and, therefore, undesirable. In many cases the welt is supposed to be fairly innocuous to the touch. A second kind of welt cord is made of cellulose filler material with a braided jacket. As discussed below, the cellulose welt cord has previously been made more fire resistant by incorporating a strip of foil or other heat conductive member into the cord along its longitudinal length.
In one prior construction as disclosed in U.S. Pat. No. 4,598,622 dated Jul. 8, 1986 entitled COMBUSTION INHIBITING CONSTRUCTION OF A WELT CORD, the cellulose welt cord has been made more fire retardant by incorporating a strip of foil into the cord along its longitudinal length to conduct heat away from a point source of heat such as a cigarette so that the cellulose near the source will not reach ignition temperature. The foil strip, however, is not resilient and has a memory. As a result, it crimps when the cord is bent, distorting the cross-sectional shape of the bent cord at the bend. Thus, when the welt cord is bent around a cushion or couch corner, for example, the welt cord will bulge at the bend, making the welt look irregular and sloppily installed.
In another prior construction as disclosed in U.S. Pat. No. 4,545,283 dated Oct. 8, 1985 entitled UPHOLSTERY WELT CORD, a small diameter foamed plastic bead was incorporated into the center of a cellulose-type welt cord with an aluminum foil layer located between the cellulose and the foam bead. When such a cord is bent, the foam assists in holding the shape of the welt cord because the "memory" of the plastic core tends to restore the cord to substantially its original cross-sectional shape after bending. However, this design is not completely satisfactory in retaining the shape of the welt cord. Further, it does not eliminate another problem with the use of foils, i.e., the foil tends to break as it is being drawn into the welt cord during manufacturing. Breakage can be greatly minimized by drawing the foil slowly into the cord, but this increases production time and costs. In addition, it complicates the braiding apparatus and method by running a larger number of elements through the braider.
Still another cord construction is disclosed in U.S. Pat. No. 4,547,426 dated Oct. 15, 1985 entitled UPHOLSTERY WELT CORD, which includes a cellulose outer cover that receives and encloses a core made of a polymeric material which has a heat conductive filament extending the length of the welt cord within the core. The cellulose cover is held on the core by a jacket of threads which are braided or wound around the cord. When a smoldering object such as a cigarette is placed against the welt cord, the cigarette will slowly burn through the threads and cellulose body in the region of the smoldering cigarette and will melt a small section of core. When the heat of the cigarette reaches the heat conductive filament, the heat of the cigarette is dissipated along the filament such that the materials in the region of the heat source will not reach a temperature where they will ignite. However, this design is not completely satisfactory due to the cost of the heat conductive filament. Further, this welt cord is deemed undesirable by many users due to people receiving injuries from the filament at cord splices, as well as other protrusions. In the process of using this welt cord, when it is inadvertently stretched and then relaxed, the polymeric cord returns to its original length, but the heat conductive filament may protrude to the outside of the welt cord.
Accordingly, it is desired in the welt cord and furniture industries to have a welt cord that is easy and inexpensive to manufacture, while being flame-retardant and flexible, but able to retain the original shape of the welt cord.